South Korean activists and defectors from the North floated 200,000 leaflets by balloon over the demilitarized zone April 15, bringing news of the Arab uprisings and calling on North Koreans to overthrow the Kim Jong Il regime. April 15 is the birthday of North Korea's founder, Kim Il Sung and is a national holiday.

Friday's statement called the leafleting "a form of psychological warfare and a clear-cut war provocation. … Direct fire at the area where leaflets are let fly will be a legitimate punishment."

South Korean activists floated 300,000 more leaflets Friday, and Lee Min-bok, organizer of the campaign, said Pyongyang's anger shows it is effective.

The North also protested the firing of machine guns near the border April 15 as an "unpardonable military provocation." The South Korean Defense Ministry said it was an accident.

United Press International is a leading provider of news, photos and information to millions of readers around the globe via UPI.com and its licensing services.

With a history of reliable reporting dating back to 1907, today’s UPI is a credible source for the most important stories of the day, continually updated - a one-stop site for U.S. and world news, as well as entertainment, trends, science, health and stunning photography. UPI also provides insightful reports on key topics of geopolitical importance, including energy and security.

A Spanish version of the site reaches millions of readers in Latin America and beyond.

UPI was founded in 1907 by E.W. Scripps as the United Press (UP). It became known as UPI when after a merger with the International News Service in 1958, which was founded in 1909 by William Randolph Hearst. Today, UPI is owned by News World Communications.